Nylon fibers are well known and have achieved a great commercial success. It is also recognized that due to excellent abrasion resistance, nylon fibers are being used for the manufacture of carpets. Although nylons perform extremely well in level loop type constructions, they show poor appearance retention characteristics in the saxony type carpets as described for example in U.S. Pat. Nos. 4,882,222 and 4,839,211. Furthermore, the conventional yarns used in this type of carpet tend also to exhibit high thermal shrinkage, low stiffness and poor flammability performance, particularly for the low pile weight carpets.
In contrast to semi-crystalline or partially crystalline fiber forming polymers such as poly(ethylene terephthalate), nylon 6 or nylon 6,6, amorphous polymers show very poor fiber forming properties and therefore are not used by industry. Consequently fibers from the compositions of nylons with amorphous polymer such as poly(phenylene oxide) (PPO) are practically unknown. Their use for the spinning of fibers is limited, partly because of polymer phase segregation in the melt due to immiscibility as well as crosslinking, and degradation processes which deteriorate or disable fiber spinning process. PPO polymer, however, is well recognized in the art for the production of numerous polymer blends and alloys as described for example in U.S. Pat. No. 4,732,938. In another example, U.S. Pat. No. 5,132,365 teaches the manufacture of poly (phenylene oxide)--polyamide compositions having improved impact strength and water resistance wherein the polyamide component comprises a mixture of amorphous and crystalline polyamide along with rubbery copolymer and compatibilizing material. Other amorphous polymers known in the art are for example polysulfones, polycarbonate and polymethyl methacrylate.
Although amorphous copolyamides are known in the art, particularly in those applications where clarity or transparency of a product is desirable, they also show poor or lack of the spinnability. Depending on the chemical structure, these materials show some miscibility with nylon polymers. A typical representative of this type of polymers is a copolyamide or terephthalic acid with 2,2,4- and 2,4,4-trimethylhexamethylenediamine manufactured by Dynamit Nobel Chemicals under TROGAMID.RTM.T.
Object of the present invention was to provide a modified polyamide for the manufacture of fibers having reduced thermal shrinkage, increased stiffness, improved wear performance, decreased flammability, and excellent uniformity and processing performance.
Another object was to provide a saxony carpet manufactured by using the modified polyamide fibers.